1. Field of the Invention
The present invention relates to a method of treating samples, and particularly to a method of treating samples adapted to corrosion prevention treatment of aluminum-containing wiring materials after they have been subjected to the etching treatment.
2. Description of the Prior Art
According to a conventional method of treating aluminum-containing wiring materials as disclosed in, for example, Japanese Patent Publication No. 41766/1983, a semiconductor wafer on which an aluminum-copper alloy film is formed is set in a reactive sputter-etching apparatus, the aluminum-copper alloy film is patterned using a plasma of such a gas as BCl.sub.3, CCl.sub.4, PCl.sub.3, BBr.sub.3 or the like, a hydrogen plasma is generated in the same apparatus, and the patterned aluminum-copper alloy film is exposed to the hydrogen plasma so as to be anti-corrosion treated.
In the above conventional technology, however, no attention has been given to removing residual or adhered matter after the etching treatment. In carrying out the etching treatment, in general, the aluminum-containing wiring material (hereinafter referred to as "wiring film") is masked with a photoresist or the like. The wiring film, in this case, may be aluminum-containing films (Al, Al-Si, Al-Cu, Al-Si-Cu, etc.) and laminated wiring films such as aluminum-containing film+barrier metal, cap metal, reflection-preventing film+aluminum-containing film+barrier metal. (The barrier metal is composed of TiW, TiN or the like, and is provided between the silicon substrate and the aluminum-containing film, in order to prevent defective junction due to mutual diffusion of the silicon substrate and the aluminum-containing film and to prevent the wiring resistance from increasing due to the precipitation of silicon in the aluminum-containing film. The cap metal is composed of TiW, TiN, MoSi, or the like, and is used as the uppermost layer of the wiring film of a laminated structure, or is used as the reflection-preventing film. The reflection-preventing film is formed on the aluminum film to suppress the reflection of light at the time of exposure, so that there is formed a resist pattern faithful to the mask.) The etching treatment is effected to treat the wafer on which the wiring film is formed using the plasma of a single gas of the type of halogen such as BCl.sub.3, Cl.sub.2, CCl.sub.4, SiCl.sub.4, HBr, BBr.sub.3 or the like, or a mixture gas thereof. The etching treatment is usually the one that is called reactive ion etching. With the reactive ion etching, the wiring film is etched maintaining a pattern faithful to the mask due to the interaction of radicals and ions in the plasma of the halogen-type gas, and the wiring pattern is obtained.
On the thus etched wiring pattern remains a photoresist (hereinafter referred to as "resist") which is a masking material. Halogen components in the plasma adhere on the surface of the resist during the etching and halogen components are implanted due to the bombardment of ions. On the side wall of the etched wiring pattern are adhered the halogen components during the etching or the resist components sputtered by the bombardment of ions. Moreover, aluminum component of the once etched wiring film adhere on the side walls again thereby to form a layer that is called side wall. This layer consists of such components as aluminum, chlorine, carbon, hydrogen, etc. that are adhered in a random fashion.
According to the above-mentioned conventional technology, a hydrogen plasma is generated in the apparatus after the etching treatment, and the patterned aluminum-copper film is exposed to the hydrogen plasma so that the aluminum-copper alloy film is anticorrosion-treated. In the treatment with hydrogen plasma, the halogen components adhered to the surfaces between the resist and the wiring pattern or adhered to the portions very close to these surfaces, undergo the reaction with hydrogen in the hydrogen plasma and can be removed as hydrogen chloride (HCl) or hydrogen bromide (HBr). However, the halogen components retaining in the resist and in the side walls are not allowed to come in contact with the hydrogen plasma and cannot be removed. Therefore, corrosion easily takes place in the wiring film due to the local battery action between the wiring film materials (between different metals) of the laminated structure or due to halogen components in the side wall (hereinafter referred to as "residual adhered matter").
Japanese Patent Laid-Open No. 43132/1987 can be cited as a prior art related to the present invention. This prior art discloses a method of plasma treatment to remove organic film (resist) on the silicon substrate in the plasma of an oxygen gas obtained by adding a compound containing at least carbon or oxygen to the oxygen, e.g., by adding methanol (CH.sub.3 OH) to the oxygen. According to this prior art, the rate of removing resist is increased (relative to the treatment using the oxygen gas plasma) and damage is prevented owing to the treatment with the plasma of a gas obtained by adding methanol (CH.sub.3 OH) to the oxygen (O.sub.2). However, this prior art is quite silent about the prevention of corrosion of the wiring film (aluminum-containing wiring material).
According to another prior art disclosed in Japanese Patent Publication No. 30268/1987, the aluminum film or the aluminum alloy film is etched using a halogen compound gas, and is then subjected to the anticorrosion treatment using the plasma of a mixture gas consisting of fluorocarbon (CF.sub.4) and oxygen (O.sub.2) without taking the aluminum film or the aluminum alloy film out of the container.